Accession Number:

ADA222390

Title:

An Adaptive Grid Algorithm for Nonequilibrium Hypersonic Flows

Descriptive Note:

Final rept. Sep 1987-Aug 1989

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF AERONAUTICS AND ASTRONAUTICS

Report Date:

1990-04-01

Pagination or Media Count:

158.0

Abstract:

The use of unstructured, adaptive, embedded grids has been applied to hypersonic nonequilibrium CFD problems. Grid adaptation was accomplished by sub- dividing computational cells for 2-D and axisymmetric blunt body configurations. The high temperature gas mixture was described by Lighthills dissociating gas model which was extended to include multiple coupled reaction paths in both viscous and inviscid flows. Nis finite volume Lax-Wendroff scheme was used to integrate the governing equations. This algorithm was extended to include shock fitting and adaptation on general, unstructured, time dependent grids. The explicit real-gas algorithm and shock fitting procedure were validated by comparisons with experimental and computational results for perfect gas, dissociating gas, and multiple reaction cases. These comparisons also emphasized the importance of chemical length scale effects in predicting nonequilibrium gas behavior. Such effects were linked not only to species concentration profiles throughout the shock layer, but also to the excess production of Nitric Oxide frequently reported off the symmetry plane in reacting air blunt body flows. A detailed study of basic nonequilibrium flow phenomena has been completed for freestream Mach numbers from 10 to 15 over blunted cones and wedges. These flows demonstrated degrees of nonequilibrium ranging from nearly frozen to near equilibrium. In all cases the adaptive procedure correctly located and resolved perfect gas and nonequilibrium features. Adaptation was shown to be particularly useful in capturing the steep chemical gradients which appear within the shock layer.

Subject Categories:

  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE